From 834a72ac74cf4ff07ba6215545dba3db578f8a07 Mon Sep 17 00:00:00 2001
From: Chris Lattner <sabre@nondot.org>
Date: Fri, 25 Jul 2008 23:18:17 +0000
Subject: [PATCH] Fix rdar://6095136, various crashes with incomplete enum
 types.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@54074 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/Basic/DiagnosticKinds.def |  1 +
 lib/AST/Type.cpp                        | 13 ++++++++-----
 lib/Sema/SemaStmt.cpp                   |  8 +++++++-
 test/Sema/enum.c                        | 15 +++++++++++++++
 4 files changed, 31 insertions(+), 6 deletions(-)

diff --git a/include/clang/Basic/DiagnosticKinds.def b/include/clang/Basic/DiagnosticKinds.def
index d7698d2901..71798a2389 100644
--- a/include/clang/Basic/DiagnosticKinds.def
+++ b/include/clang/Basic/DiagnosticKinds.def
@@ -961,6 +961,7 @@ DIAG(err_typecheck_expression_not_modifiable_lvalue, ERROR,
      "expression is not assignable")
 DIAG(err_typecheck_incomplete_type_not_modifiable_lvalue, ERROR,
      "incomplete type '%0' is not assignable")
+
 DIAG(err_typecheck_duplicate_vector_components_not_mlvalue, ERROR,
      "vector is not assignable (contains duplicate components)")
 DIAG(err_typecheck_call_not_function, ERROR,
diff --git a/lib/AST/Type.cpp b/lib/AST/Type.cpp
index 0082b2f7b3..275406eaba 100644
--- a/lib/AST/Type.cpp
+++ b/lib/AST/Type.cpp
@@ -476,7 +476,8 @@ bool Type::isIntegerType() const {
     return BT->getKind() >= BuiltinType::Bool &&
            BT->getKind() <= BuiltinType::LongLong;
   if (const TagType *TT = dyn_cast<TagType>(CanonicalType))
-    if (TT->getDecl()->isEnum())
+    // Incomplete enum types are not treated as integer types.
+    if (TT->getDecl()->isEnum() && TT->getDecl()->isDefinition())
       return true;
   if (const VectorType *VT = dyn_cast<VectorType>(CanonicalType))
     return VT->getElementType()->isIntegerType();
@@ -490,8 +491,8 @@ bool Type::isIntegralType() const {
     return BT->getKind() >= BuiltinType::Bool &&
     BT->getKind() <= BuiltinType::LongLong;
   if (const TagType *TT = dyn_cast<TagType>(CanonicalType))
-    if (TT->getDecl()->isEnum())
-      return true;
+    if (TT->getDecl()->isEnum() && TT->getDecl()->isDefinition())
+      return true;  // Complete enum types are integral.
   if (const ASQualType *ASQT = dyn_cast<ASQualType>(CanonicalType))
     return ASQT->getBaseType()->isIntegralType();
   return false;
@@ -593,7 +594,7 @@ bool Type::isRealType() const {
     return BT->getKind() >= BuiltinType::Bool &&
            BT->getKind() <= BuiltinType::LongDouble;
   if (const TagType *TT = dyn_cast<TagType>(CanonicalType))
-    return TT->getDecl()->isEnum();
+    return TT->getDecl()->isEnum() && TT->getDecl()->isDefinition();
   if (const VectorType *VT = dyn_cast<VectorType>(CanonicalType))
     return VT->getElementType()->isRealType();
   if (const ASQualType *ASQT = dyn_cast<ASQualType>(CanonicalType))
@@ -617,7 +618,9 @@ bool Type::isScalarType() const {
   if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
     return BT->getKind() != BuiltinType::Void;
   if (const TagType *TT = dyn_cast<TagType>(CanonicalType)) {
-    if (TT->getDecl()->isEnum())
+    // Enums are scalar types, but only if they are defined.  Incomplete enums
+    // are not treated as scalar types.
+    if (TT->getDecl()->isEnum() && TT->getDecl()->isDefinition())
       return true;
     return false;
   }
diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp
index 1462d3d57c..a4e8946b45 100644
--- a/lib/Sema/SemaStmt.cpp
+++ b/lib/Sema/SemaStmt.cpp
@@ -25,6 +25,12 @@ using namespace clang;
 Sema::StmtResult Sema::ActOnExprStmt(ExprTy *expr) {
   Expr *E = static_cast<Expr*>(expr);
   assert(E && "ActOnExprStmt(): missing expression");
+  
+  // C99 6.8.3p2: The expression in an expression statement is evaluated as a
+  // void expression for its side effects.  Conversion to void allows any
+  // operand, even incomplete types.
+  
+  // Same thing in for stmt first clause (when expr) and third clause.
   return E;
 }
 
@@ -536,7 +542,7 @@ Sema::ActOnForStmt(SourceLocation ForLoc, SourceLocation LParenLoc,
     
     if (!SecondType->isScalarType()) // C99 6.8.5p2
       return Diag(ForLoc, diag::err_typecheck_statement_requires_scalar,
-               SecondType.getAsString(), Second->getSourceRange());
+                  SecondType.getAsString(), Second->getSourceRange());
   }
   return new ForStmt(First, Second, Third, Body, ForLoc);
 }
diff --git a/test/Sema/enum.c b/test/Sema/enum.c
index 2a20d3d7d5..8d184d3d85 100644
--- a/test/Sema/enum.c
+++ b/test/Sema/enum.c
@@ -33,3 +33,18 @@ int test2(int i)
 union u0;    // expected-error {{previous use is here}}
 enum u0 { U0A }; // expected-error {{error: use of 'u0' with tag type that does not match previous declaration}}
 
+
+// rdar://6095136
+extern enum some_undefined_enum ve2; // expected-warning {{ISO C forbids forward references to 'enum' types}}
+
+void test4() {
+  for (; ve2;) // expected-error {{statement requires expression of scalar type}}
+    ;
+  (_Bool)ve2;  // expected-error {{statement requires expression of scalar type}}
+
+  for (; ;ve2)
+    ;
+  (void)ve2;
+  ve2;
+}
+
-- 
2.40.0